Describe ube sound vs solid state

^Them it would appear that the Mac 30 is not capable of adapting to the variable impedance swings of typical loudspeakers without deviating from linear frequency response?

No, not at all, unless the amp is set up on the wrong tap.

If the speaker is 4 ohms in the bass and 8 or 16 ohms in the highs, you put it on the 4 ohm tap and the bass will be correct as well as the highs. It will be just as flat as a transistor amp on the same speaker.

^So for example; with a dynamic loudspeaker speaker with a nominal 8 Ohm load with dips to 4 Ohms and peaks to 16 Ohms; the Mac 30 will double it's power output into 4 Ohms and halve it's power output into 16 Ohms?

^^ The nature of the dips should be examined. If at crossover points which is a common point of a dip, they will be of no consequence.

The amplifier power will be signal dependent of course, and the output into 8 ohms will be 1/2 of its 4 ohm power (30 watts) and 1/4 of that into 16 ohms if the signal is full bandwidth.

IOW, feedback causes an adaptive response in the amplifier.

^Well that is interesting.
I'd love to see the graphs of the tests on that amp, as I've never seen a graph of a tube amp that could demonstrate that kind of skill. I'm very curious as to what it's distortion levels were like as it went through various impedances. It still seems as though it wouldn't need the various impedance output taps? Why wouldn't the cross-over points matter? Is that how the amp would behave when connected to the 8 Ohm tap (the given speakers nominal impedance).

Actually there are a good number of tube amps that can do that. Any Mac for example. Ever hear of the Wolcott? Henry made a point of advertising that his amp could operate as a true voltage source.

All amps have higher distortion into lower impedances. As far as that goes, there is no argument for a 4 ohms speaker in the world of high end, not if sound quality is your goal. Why force all amps to have higher distortion??

You still need the impedance taps otherwise you may not be getting the most out of the amp.